Apparatus for increasing blank holding pressure during drawing operation



July 15, 1958 APPARATUS FOR INCREASING BLANK HOLDING PRESSURE DURINGDRAWING OPERATION Filed 001;. 25, 1952 J. A. KITZINGER v 2,843,071

United States Patent 0,

APPARATUS FOR INCREASING BLANK HOLDING PRESSURE DURING DRAWING OPERATIONJoseph A. Kitzinger, Spring Lake, Mich., assignor to Borg-:WarnerCorporation, Chicago, 111., a corporation of Illinois ApplicationOctober 25, 1952, Serial No. 316,855

1 Claim. (Cl. 113-46) This invention relates, in general, to thefabrication of refrigerator cabinet liners formed of sheet metal by drawdie operations, and is more particularly concerned with the mechanicalpress mechanism employed in the format1on of refrigerator liners from asingle sheet metal blank.

This is a continuation-in-part of my now abandoned patent applicationSerial No. 766,623, filed August 6, 1947, entitled Apparatus forIncreasing Blank Holding Pressure During Drawing Operation.

Heretofore, because of the large size of the refrigerator liners andbecause of the deep drawing operations required, the old method offabricating refrigerator liners consisted of a three-piece tank whichwas suitably welded together to define a refrigerator liner. Thisprocedure in fabricating such refrigerator liners produced arefrigerator liner lacking in rigidity and having surfaces hard to cleanafter welding and having a welded corner which was definitely hard tocover with paint or porcelain because of the roughened surfaces producedin welding operations.

Accordingly, an important object and accomplishment of the invention isthe provision of a mechanism adaptable to form from a single sheet metalblank, a refrigerator cabinet liner having a continuous, uninterruptedmetal surface free from welded slits, flanges and patches, therebysecuring substantial economies in manufacture and an improvedappearance, while eliminating enameling flaws resulting from thedifficulty in providing a clear, uniform baked enamel or other desirablesurface finish, due to the welds heretofore employed in the foundationmaterial.

Another object of the invention is to provide a refrigerator liner ascontemplated herein which overcomes the ditficulties and eliminates manyof the objections and complicated operations involved in prior practice.

The invention seeks, as a further object and accomplishment, to providea refrigerator cabinet liner as contemplated herein and characterized byan arrangement to more advantageously and satisfactorily perform thefunction required of it and adapted to provide a unit which willsuccessfully combine the factors of structural simplicity anddurability, and yet be economical to manufacture.

A further object and accomplishment of the invention is to provide arefrigerator liner as contemplated herein which may be of simpleconstruction without welding and which refrigerator liner may be readilycoated with a preferably acid-resisting finish such as, for example,enamel or plastic so that the resulting coating is uniform in appearanceand characteristics and a refrigerator liner which is free from flawswhich result if welded areas are present in the sheet metal base.

The invention has for a further object, the provision of a refrigeratorliner which may be formed in a single drawing operation regardless ofthe fact that such refrigerator liners require a substantially deepdrawing operation and which refrigerator liner, at the same time,provides smooth regular well-rounded corners at all junctures of thewall in the inner portions of the liner which has been long 2,843,071Patented July 15, 1958 ice.

desired and has heretofore been impossible with presently knownpractices.

Additional objects, features and advantages of the invention disclosedherein will be apparent to persons skilled in the art after theconstruction and operation are understood from the within description.

It is preferred to accomplish the various objects of this invention andto practice the same in substantially the manner hereinafter fullydescribed and as more particularly pointed out in the appended claim,reference being had to the accompanying drawing which forms a part ofthis specification, wherein:

Fig. 1 is a perspective view of a refrigerator cabinet liner embodyingthe features of the present invention;

Fig. 2 is a sectional elevational view taken in the plane of line 2-2 ofFig. 4 showing a mechanical drawing die which may be employed in theformation of the refrigerator liner depicted in Fig. 1, said die beingillustrated in a position before the actual drawing operation;

Fig. 3 is a view similar to Fig. 2, but shown in a final position of thedrawing operation;

Fig. 4 is a top plan view of the mechanical drawing die depicted in Fig.2 and illustrates the relative disposition of the spring elements whichcomprise an important feature of the invention contemplated herein, thisview being taken substantially on the plane of the line 4--4 in Fig. 3;and

Fig. 5 is a fragmentary sectional view of the spring elements and meansfor supporting the spring retainers, this view being taken substantiallyon the plane of the line 5-5 in Fig. 4.

The drawing is to be understood as being more or less of a schematiccharacter for the purpose of illustrating and disclosing a typical orpreferred form of the improvements contemplated herein, and in thedrawing like reference characters identify the same parts in the severalviews.

In the exemplary embodiment of the invention depicted in Figs. 1, 2, 3and 4, I have illustrated a mechanical die press designated initsentirety by the numeral 20 and generally comprising a punch 21 formed todefine a substantially rectangular shape and having a flange pro jectingportion 22, the function of which will be hereinafter described, afemale die member 23 formed by any approved practicein amanner'complementary to said punch and being adaptable to receiveportions of the punch during the drawing operations contemplated herein,a blank support ring 24 adaptable to carry a metal blank such as at Aduring the initial drawing operation, said support ring being providedwith suitable recesses 25, 26, 27 and 28 each adaptable to receive aspring retaining member 30, 31, 32 and 33, respectively, and each ofsaid spring retaining members having operatively disposed thereincompression springs 35 of suitable tension and thickness to exert anadditional sixty-ton clamping pressure on the formed flange of therefrigerator liner during approximately the last three-eighths inch ofdrawing, thereby'restricting the metal on the two sides and the ends andgiving a stretching action on these areas while allowing metal in the'cornersto flow, thereby preventing contortion of the sides and endsusually found in prior art practices. Thus, the result is the provisionof a refrigerator liner B shown in Fig. 1 as having straight sides andends and, more important, is the provision of a refrigerator linerhaving a continuous uninterrupted metal surface free from welded slits,flanges and patches, thereby securing substantial economies inmanufacture and improved appearance, while eliminating enameling flawsresulting in the difliculty in preventing a clear uniform baked enamelor other desirable surface finish ,to the welds heretofore employed infoundation material when forming such refrigerator liners.

Adverting to Fig. 4, it can be seen that I have disposed the springretaining means on each'side and at each end of the die. It is importantto note that the corners are left free thereby permitting the metal inthe corners to flow, which results in a well-rounded corner having acontinuous uninterrupted metal surface.

The spring retainers are disposed in the recesses 25, 26, 27 and 28 in amanner to permit vertical movement with respect to the support ring 24.It is notable that such spring retainers are composed of two parts 40and 41 (Fig. 2), each part having a recess 42 and 43, respectively,adaptable to receive the spring 35.

In order to retain the retainer members 40 in the recesses there isprovided a flange 50 which permits upward movement of the retainermember 40 but resists downward movement below the area defined by theflange.

To prevent separation of the retaining members when the assembly is in aposition as shown in Fig. 2, there are provided bolt members as at 51(see Fig. having end portions respectively engaging the retainingmembers 40 and 41 as shown so as to provide restricted relative movementtherebe tween. The cavities as at 52 may be provided with a removableplug indicated at each instance by the numeral 53 to present a smoothtop surface to the retaining members 40.

It is noted that only certain of the springs 35 are provided with a rod51. For example, the springs 35 shown in Figs. 2 and 3 are not providedwith a rod. These springs are disposed intermediate the springs 35 whichsurround the rods 51 and which are further characterized by having theplugs 53 disposed immediately above the rods 51.

Thus, it is apparent from the showing of Fig. 4 that the dotted circlesindicated by the reference numerals 42 represent the projection of therecesses 42, housing the upper end of the intermediate springs 35. Theplugs 53 of course, denote those locations wherein the springs 35 havebeen provided with a rod 51.

The blank support ring 24 is movable in a vertical path but its movementis resisted by a plurality of draw pins as at 55 having their upperportion in engagement with portions of the support ring 24 and the lowerportions thereof extending into the bolster 56 wherein there is providedspring means or hydraulic means (not shown) to provide aninitialblankholder pressure.

According to the construction of the present invention, it may beobserved in Fig. 2 thatthe spring retaining means does not have anyimportant function in the initial steps of drawing operation; however,after the punch has been received into the female die member 23 which iscaused by suitable pressure being exerted upon the female die member inthe direction of the arrow 44 (Fig. 2), it can be seen that the springretainer is in contact with the projecting portion 22 of the punch 21.As additional downward pressure is applied during the last three-eighthsinch of drawing the spring retainers are positioned between the flange45 of the refrigerator liner and the projecting portion 22 of the punch21, whereby because of the natural action of the compression spring 35,an additional sixty-ton clamping pressure is exerted upon the flange 45in the areas as hereinbefore described which will restrict the metal onthe two sides and ends and give a stretching action on these areas whileallowing metal in the corners to flow thereby preventing contortion ofthe sides and ends usually found in prior art practices.

The operation of the device may be as follows: normally the female diemember is in a raised position (not shown), and the blank A may beplaced in position upon the support ring 24, as shown in Fig. 2. Forceis then applied to urge the female die member 23 downwardly which willforce the punch 21 to enter the complementary portions of the female diemember and proceed to form the refrigerator liner as shown in Fig. 3.During the last steps of the drawing operation it may be observed thatthe spring retainers are in contact with the projecting portion 22 ofthe punch 21 thereby tending to compress the two members 40 and 41 ofthe spring retainers, which compression is resisted by the compressionsprings 35 resulting in an additional sixty-ton clamping pressure on theformed flange 45 in the areas hereinbefore described during the lastthree-eighths inch of drawing, thereby restricting the metal on the twosides and ends and giving a stretching action on these areas whileallowing the metal in the corners to flow. It is important to understandthat the drawing operations contemplated herein are deep draw operationsas distinguished from the usual drawing operations in prior artpractices for such shallow drawing operations for smaller units.

The mechanisms disclosed herein may be advantageously employed in massproduction manufacturing methods where quick and easy drawing operationsresult in economies in manufacture which determine the final cost of theunits drawn.

From the foregoing disclosure, it may be observed that I have provided arefrigerator liner and mechanism for forming the same which may besummarized as follows:

(1) Structurally simple, efficient and durable;

(2) Economical to manufacture and readily adaptable to mass productionmanufacturing principles; and

(3) The provision of a refrigerator liner and mechanism for forming thesame which may be of simple construction and which refrigerator linermay be formed of a one-piece metal blank without welding and may bereadily coated with a preferably acid-resisting finish so that theresulting coating is uniform in appearance and characteristic and arefrigerator liner which is free from flaws which result if welded areasare present in the sheet metal base.

While I have illustrated a preferred embodiment of my invention, manymodifications may be made without departing from the spirit of theinvention, and I do not wish to be limited to the precise details ofconstruction set forth, but wish to avail myself of all changes withinthe scope of the appended claim.

I claim:

A mechanical die press for deep draw operations from a one-piece blank,comprising a rectagular punch, a rectangular female die member arrangedto receive portions of said punch during the drawing operation, movablerectangular support means arranged to carry the metal blank during theinitial drawing operation, means in engagement with said support meansto resist movement of said rectangular support means to provide initialblankholder pressure, said support means being arranged to substantiallysurround the punch and to cooperate with the die member for clamping theblank during the drawing operation, a plurality of retaining memberseach member being composed of two cup-shaped members and a spring witheach end disposed in the recess of each cupshaped member to normallymaintain said cup-shaped members in spaced relation, retaining means ineach recess to limit the separation of said cup-shaped members, saidretaining members being disposed in the support means adjacent the punchand at a distance from the corners of the support means with the uppercup-shaped member of each retaining member being disposed on a levelwith the upper surface of the support means and the lower cup-shapedmember projecting below the support means, and abutment means arrangedaround the bottom of the punch whereby the lower cup-shaped member willcontact the abutment means during the last fraction of an inch ofdrawing and apply localized clamping pressure by the compression of thesprings and retaining members so that metal in the blank is restrictedat the portions of the blank engaged by the retaining members and forcedto flow at the corner portions of the blank.

(References on following page) Refernces Cited in the file of thispatent UNITED STATES PATENTS Opsal Mar. 2, 1909 Klocke Nov. 27, 1923 5MacGregor Nov. 4, 1930 Spatta Aug. 22, 1933

